Portable digital devices such as digital cameras, MP3 players, color mobile phones, personal data assistants (PDAs), etc., typically utilize memory cards (i.e., MultiMedia cards, Secure Digital (SD) cards) to store data. These memory cards typically have non-volatile storage characteristics.
In general, a memory card system may include a host and a memory card. The memory card includes a memory controller and a memory core. The memory controller manages an overall operation for interfacing with the host and the memory core. The memory core usually employs a NAND flash memory. NAND flash memory devices can be classified into types: single-level cell (SLC) devices and multi-level cell (MLC) devices.
Bad blocks with data storage errors may be generated when writing data into the NAND flash memory, due to variations in processing conditions, voltage levels of selected word lines, operation voltages, and temperature. A memory card replaces a bad block with a usable block that is assigned to a predetermined region of the NAND flash memory, by means of a flash translation layer (FTL) included in the memory controller. This management of bad block is carried out through an address mapping process by the memory controller.
The address mapping is conducted by an FTL, which is stored in the memory controller. The FTL functions to map a logical address, which is generated from the host during a writing operation, into a physical address of the flash memory that has been erased. The FTL may be formed of software or hardware in the pattern of firmware. Examples of address mapping carried out by FTL are disclosed in U.S. Pat. No. 5,404,485 entitled “FLASH FILE SYSTEM”, U.S. Pat. No. 5,937,485 entitled “FLASH FILE SYSTEM OPTIMIZED FOR PAGE-MODE FLASH TECHNOLOGIES”, and U.S. Pat. No. 6,381,176 entitled “METHOD OF DRIVING REMAPPING IN FLASH MEMORY AND FLASH MEMORY ARCHITECTURE SUITABLE THEREOF.” This address mapping information is stored in a hidden area of the NAND flash memory as metadata. As an address mapping operation is carried out whenever data is written in the NAND flash memory, such metadata is updated and stored in the NAND flash memory every data input.
The memory card may store updated metadata and host input data into the NAND flash memory whenever data is input from the host. Generally, the NAND flash memory is longer than an SRAM or NOR flash memory in terms of data storage time. In storing data into the memory card, the host sends the memory card a single-block-write command if the data to be transferred is 512 bytes or a multiple-block-write command if the data to be transferred is a plurality of 512 bytes. If the memory card includes an MLC NAND flash memory and receives the single-block-write command from the host, the memory card stores 512-byte data, which is input from the host, into a page of the MLC NAND flash memory that is designated with an address by the host. If the host continues to transfer the single-block-write command, the host designates successive addresses and transfers the 512-byte data until the assigned page of the MLC NAND flash memory is full of data. If a unit page of an MLC NAND flash memory has data capacity of 2 K bytes, the host transfers 512-byte data four times. But, because a unit page of the MLC NAND flash memory is limited as being available for one-time writing, 512-byte data input from the host is stored in another page different from the page storing the previous 512-byte data. Thus, the host stores four groups of 512-byte data in four individual pages, respectively, of the MLC NAND flash memory in substance.
The 512-bytes of data each stored in the four pages of the MLC NAND flash memory by the memory controller are all stored in a single page of the MLC NAND flash memory. After then, the memory controller erases the 512-byte data stored in the four pages, arranging the data input from the host. Therefore, the memory card typically must execute a complicated procedure of operation for storing data into the MLC NAND flash memory when the host conducts the single-block-write command. Thus, the memory card storing data in the MLC NAND memory operates with a longer data storage time. As a result, the memory card may have a long data storage time as a whole because metadata is updated and stored in the NAND flash memory-every time data is input from the host. Further, including the MLC NAND flash memory, the memory card has a longer data storage time because of the necessity of conducting a complicated procedure of operation for storing data into the MLC NAND flash memory from the host. Such an extension of the whole data storage time causes degradation of operational performance in the memory card.